linux-kernel - Re: [PATCH v8 17/25] x86/resctrl: Add the interface to assign/update counter assignment

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Message-ID: <379acb61-0afb-457b-85d8-916f23b39e4b@intel.com>
Date: Mon, 21 Oct 2024 08:31:29 -0700
From: Reinette Chatre <reinette.chatre@...el.com>
To: <babu.moger@....com>, <corbet@....net>, <fenghua.yu@...el.com>,
	<tglx@...utronix.de>, <mingo@...hat.com>, <bp@...en8.de>,
	<dave.hansen@...ux.intel.com>
CC: <x86@...nel.org>, <hpa@...or.com>, <paulmck@...nel.org>,
	<rdunlap@...radead.org>, <tj@...nel.org>, <peterz@...radead.org>,
	<yanjiewtw@...il.com>, <kim.phillips@....com>, <lukas.bulwahn@...il.com>,
	<seanjc@...gle.com>, <jmattson@...gle.com>, <leitao@...ian.org>,
	<jpoimboe@...nel.org>, <rick.p.edgecombe@...el.com>,
	<kirill.shutemov@...ux.intel.com>, <jithu.joseph@...el.com>,
	<kai.huang@...el.com>, <kan.liang@...ux.intel.com>,
	<daniel.sneddon@...ux.intel.com>, <pbonzini@...hat.com>,
	<sandipan.das@....com>, <ilpo.jarvinen@...ux.intel.com>,
	<peternewman@...gle.com>, <maciej.wieczor-retman@...el.com>,
	<linux-doc@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<eranian@...gle.com>, <james.morse@....com>
Subject: Re: [PATCH v8 17/25] x86/resctrl: Add the interface to assign/update
 counter assignment

Hi Babu,

On 10/21/24 7:40 AM, Moger, Babu wrote:
> On 10/18/24 10:59, Reinette Chatre wrote:
>> On 10/17/24 3:56 PM, Moger, Babu wrote:
>>> On 10/15/2024 10:25 PM, Reinette Chatre wrote:
>>>> On 10/9/24 10:39 AM, Babu Moger wrote:
>>
>>>>> + */
>>>>> +int rdtgroup_assign_cntr_event(struct rdt_resource *r, struct rdtgroup *rdtgrp,
>>>>> +                   struct rdt_mon_domain *d, enum resctrl_event_id evtid)
>>>>> +{
>>>>> +    int index = MBM_EVENT_ARRAY_INDEX(evtid);
>>>>> +    int cntr_id = rdtgrp->mon.cntr_id[index];
>>>>> +    int ret;
>>>>> +
>>>>> +    /*
>>>>> +     * Allocate a new counter id to the event if the counter is not
>>>>> +     * assigned already.
>>>>> +     */
>>>>> +    if (cntr_id == MON_CNTR_UNSET) {
>>>>> +        cntr_id = mbm_cntr_alloc(r);
>>>>> +        if (cntr_id < 0) {
>>>>> +            rdt_last_cmd_puts("Out of MBM assignable counters\n");
>>>>> +            return -ENOSPC;
>>>>> +        }
>>>>> +        rdtgrp->mon.cntr_id[index] = cntr_id;
>>>>> +    }
>>>>> +
>>>>> +    if (!d) {
>>>>> +        list_for_each_entry(d, &r->mon_domains, hdr.list) {
>>>>> +            ret = resctrl_arch_config_cntr(r, d, evtid, rdtgrp->mon.rmid,
>>>>> +                               rdtgrp->closid, cntr_id, true);
>>>>> +            if (ret)
>>>>> +                goto out_done_assign;
>>>>> +
>>>>> +            set_bit(cntr_id, d->mbm_cntr_map);
>>>>
>>>> The code pattern above is repeated four times in this work, twice in
>>>> rdtgroup_assign_cntr_event() and twice in rdtgroup_unassign_cntr_event(). This
>>>> duplication should be avoided. It can be done in a function that also resets
>>>> the architectural state.
>>>
>>> Are you suggesting to combine rdtgroup_assign_cntr_event() and rdtgroup_unassign_cntr_event()?
>>
>> No. My comment was about the following pattern that is repeated four times:
>> 	...
>> 	ret = resctrl_arch_config_cntr(...)
>> 	if (ret)
>> 		...
>> 	set_bit()/clear_bit()
>> 	...
>>
> 
> ok.
> 
> 
>>> It can be done. We need a flag to tell if it is a assign or unassign.
>>
>> There is already a flag that is used by resctrl_arch_config_cntr(), the same parameters
>> as resctrl_arch_config_cntr() can be used for a wrapper that just calls
>> resctrl_arch_config_cntr() directly and uses that same flag to
>> select between set_bit() and clear_bit(). This wrapper can then also include
>> the reset of architectural state.
> 
> ok. Got it, It will look like this.
> 
> 
> +/*
> + * Wrapper to configure the counter in a domain.
> + */

Please replace comment with a description of what the function does.

> +static int rdtgroup_config_cntr(struct rdt_resource *r,struct

While it keeps being a challenge to get naming right I do think this
can start by replacing "rdtgroup" with "resctrl" (specifically,
"rdtgroup_config_cntr() -> resctrl_config_cntr()") because, as seen
with the parameters passed, this has nothing to do with rdtgroup.

> rdt_mon_domain *d,
> +                               enum resctrl_event_id evtid, u32 rmid, u32
> closid,
> +                               u32 cntr_id, bool assign)
> +{
> +       int ret;
> +
> +       ret = resctrl_arch_config_cntr(r, d, evtid, rmid, closid, cntr_id,
> assign);
> +       if (ret)
> +               return ret;
> +
> +       if (assign)
> +               __set_bit(cntr_id, d->mbm_cntr_map);
> +       else
> +               __clear_bit(cntr_id, d->mbm_cntr_map);
> +
> +       /*
> +        * Reset the architectural state so that reading of hardware
> +        * counter is not considered as an overflow in next update.
> +        */
> +       resctrl_arch_reset_rmid(r, d, closid, rmid, evtid);
> +
> +       return ret;
> +}
> +

Yes, this looks good. Thank you.

Reinette